U.S. patent application number 14/489113 was filed with the patent office on 2015-05-07 for systems and methods for in situ resistive heating of organic matter in a subterranean formation.
The applicant listed for this patent is Chen Fang, Federico G. Gallo, Nazish Hoda, Michael W. Lin, William P. Meurer. Invention is credited to Chen Fang, Federico G. Gallo, Nazish Hoda, Michael W. Lin, William P. Meurer.
Application Number | 20150122491 14/489113 |
Document ID | / |
Family ID | 53006141 |
Filed Date | 2015-05-07 |
United States Patent
Application |
20150122491 |
Kind Code |
A1 |
Meurer; William P. ; et
al. |
May 7, 2015 |
Systems and Methods for In Situ Resistive Heating of Organic Matter
in a Subterranean Formation
Abstract
A method for pyrolyzing organic matter in a subterranean
formation includes powering a first generation in situ resistive
heating element within an aggregate electrically conductive zone at
least partially in a first region of the subterranean formation by
transmitting an electrical current between a first electrode pair
in electrical contact with the first generation in situ resistive
heating element to pyrolyze a second region of the subterranean
formation, adjacent the first region, to expand the aggregate
electrically conductive zone into the second region, wherein the
expanding creates a second generation in situ resistive heating
element within the second region and powering the second generation
in situ resistive heating element by transmitting an electrical
current between a second electrode pair in electrical contact with
the second generation in situ resistive heating element to generate
heat with the second generation in situ resistive heating element
within the second region.
Inventors: |
Meurer; William P.;
(Magnolia, TX) ; Fang; Chen; (Houston, TX)
; Gallo; Federico G.; (Houston, TX) ; Hoda;
Nazish; (Houston, TX) ; Lin; Michael W.;
(Bellaire, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Meurer; William P.
Fang; Chen
Gallo; Federico G.
Hoda; Nazish
Lin; Michael W. |
Magnolia
Houston
Houston
Houston
Bellaire |
TX
TX
TX
TX
TX |
US
US
US
US
US |
|
|
Family ID: |
53006141 |
Appl. No.: |
14/489113 |
Filed: |
September 17, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61901234 |
Nov 7, 2013 |
|
|
|
Current U.S.
Class: |
166/250.02 ;
166/302 |
Current CPC
Class: |
E21B 36/04 20130101;
E21B 43/2401 20130101 |
Class at
Publication: |
166/250.02 ;
166/302 |
International
Class: |
E21B 43/24 20060101
E21B043/24; E21B 36/04 20060101 E21B036/04; E21B 47/06 20060101
E21B047/06; E21B 43/14 20060101 E21B043/14 |
Claims
1. A method for pyrolyzing organic matter in a subterranean
formation, the method comprising: powering a first generation in
situ resistive heating element within an aggregate electrically
conductive zone at least partially in a first region of the
subterranean formation by transmitting an electrical current
between a first electrode pair in electrical contact with the first
generation in situ resistive heating element to pyrolyze a second
region of the subterranean formation, adjacent the first region, to
expand the aggregate electrically conductive zone into the second
region, wherein the expanding creates a second generation in situ
resistive heating element within the second region; and powering
the second generation in situ resistive heating element by
transmitting an electrical current between a second electrode pair
in electrical contact with the second generation in situ resistive
heating element to generate heat with the second generation in situ
resistive heating element within the second region, wherein at
least one of the second electrode pair extends within the second
region.
2. The method of claim 1, further comprising pyrolyzing the first
region of the subterranean formation to create the first generation
in situ resistive heating element within the first region.
3. The method of claim 2, further comprising placing in the
subterranean formation at least one electrode well prior to
creating the first generation in situ resistive heating element,
wherein the electrode well is configured to contain at least one
electrode of the first electrode pair or the second electrode
pair.
4. The method of claim 2, wherein the placing in the subterranean
formation at least one electrode well includes placing two
electrodes within the electrode well, and wherein the electrode
well includes a wellbore heater between the two electrodes.
5. The method of claim 2, further comprising placing at least one
electrode of the second electrode pair into electrical contact with
the second region prior to creating the first generation in situ
resistive heating element.
6. The method of claim 2, wherein the pyrolyzing the first region
includes increasing an average electrical conductivity of the first
region.
7. The method of claim 2, wherein the pyrolyzing the first region
results in an average electrical conductivity of the first region
of at least 10.sup.-4 S/m.
8. The method of claim 1, further comprising placing at least one
electrode of the second electrode pair into electrical contact with
the second region prior to creating the second generation in situ
resistive heating element.
9. The method of claim 1, further comprising placing in the
subterranean formation at least one electrode well prior to
creating the second generation in situ resistive heating element,
wherein the electrode well is configured to contain at least one
electrode of the first electrode pair or the second electrode
pair.
10. The method of claim 1, wherein the powering the first
generation in situ resistive heating element includes expanding the
aggregate electrically conductive zone into electrical contact with
at least one electrode of the second electrode pair.
11. The method of claim 1, wherein the powering the first
generation in situ resistive heating element includes establishing
electrical contact between the aggregate electrically conductive
zone and at least one electrode of the second electrode pair.
12. The method of claim 1, wherein the powering the first
generation in situ resistive heating element includes increasing
the degree of electrical contact between the aggregate electrically
conductive zone and at least one electrode of the second electrode
pair.
13. The method of claim 1, wherein at least one electrode of the
first electrode pair includes an elongated contact portion, wherein
the powering the first generation in situ resistive heating element
includes expanding the aggregate electrically conductive zone along
a length of the elongated contact portion.
14. The method of claim 1, further comprising ceasing the powering
the first generation in situ resistive heating element before the
powering the second generation in situ resistive heating
element.
15. The method of claim 1, further comprising ceasing the powering
the first generation in situ resistive heating element during the
powering the second generation in situ resistive heating
element.
16. The method of claim 1, wherein the powering the first
generation in situ resistive heating element includes regulating
expansion of the aggregate electrically conductive zone by
controlling at least one of a duration of the powering, a magnitude
of electrical power, and a magnitude of electrical current.
17. The method of claim 1, wherein the powering the second
generation in situ resistive heating element includes regulating
expansion of the aggregate electrically conductive zone by
controlling at least one of a duration of the powering, a magnitude
of electrical power, and a magnitude of electrical current.
18. The method of claim 1, wherein the powering the first
generation in situ resistive heating element includes pyrolyzing a
plurality of second regions of the subterranean formation, each
adjacent the first region, to create a second generation in situ
resistive heating element within each second region, wherein the
pyrolyzing the plurality of second regions expands the aggregate
electrically conductive zone into each of the second regions; and
wherein the powering the second generation in situ resistive
heating element includes powering at least two second generation in
situ resistive heating elements by transmitting an electrical
current between at least two second electrode pairs, each second
electrode pair in electrical contact with a distinct second
generation in situ resistive heating element, to heat the second
regions.
19. The method of claim 18, wherein the pyrolyzing the plurality of
second regions includes expanding the aggregate electrically
conductive zone into electrical contact with at least one electrode
of each second electrode pair.
20. The method of claim 18, wherein the pyrolyzing the plurality of
second regions includes establishing electrical contact between the
aggregate electrically conductive zone and at least one electrode
of each second electrode pair.
21. The method of claim 18, wherein the pyrolyzing the plurality of
second regions includes increasing the degree of electrical contact
between the aggregate electrically conductive zone and at least one
electrode of each second electrode pair.
22. The method of claim 1, further comprising determining a desired
geometry of the aggregate electrically conductive zone prior to the
powering the first generation in situ resistive heating element, at
least partially based on data relating to at least one of the
subterranean formation and the organic matter in the subterranean
formation.
23. The method of claim 1, further comprising determining a desired
geometry of the aggregate electrically conductive zone prior to the
powering the first generation in situ resistive heating element, at
least partially based on data relating to the organic matter in the
subterranean formation.
24. The method of claim 1, further comprising monitoring a
parameter while powering the first generation in situ resistive
heating element, wherein the parameter includes geophysical data
relating to at least one of a shape, an extent, a volume, a
composition, a density, a porosity, a permeability, an electrical
conductivity, an electrical property, a temperature, and/or a
pressure of at least a portion of the subterranean formation; and
further wherein the method includes ceasing powering the first
generation in situ resistive heating element at least partially
based on the parameter.
25. The method of claim 1, further comprising monitoring a
parameter while powering the first generation in situ resistive
heating element, wherein the parameter includes at least one of the
duration of applied electrical power, the magnitude of electrical
power applied, and the magnitude of electrical current transmitted,
and further wherein the method includes ceasing powering the first
generation in situ resistive heating element at least partially
based on the parameter.
26. The method of claim 1, wherein the powering the first
generation in situ resistive heating element and the powering the
second generation in situ resistive heating element include
producing at least one of liquid hydrocarbons, gaseous
hydrocarbons, shale oil, bitumen, pyrobitumen, bituminous coal, and
coke.
27. The method of claim 1, wherein the pyrolyzing the second region
includes increasing an average electrical conductivity of the
second region.
28. The method of claim 1, wherein the pyrolyzing the second region
results in an average electrical conductivity of the second region
of at least 10.sup.-4 S/m.
29. The method of claim 1, wherein the pyrolyzing the second region
includes decreasing an average electrical conductivity of the first
generation in situ resistive heating element.
30. A method for pyrolyzing organic matter in a subterranean
formation, the method comprising: transmitting a first electrical
current in the subterranean formation between a first electrode
pair in electrical contact with a first generation in situ
resistive heating element; powering a first generation in situ
resistive heating element, within an aggregate electrically
conductive zone at least partially in a first region of the
subterranean formation, with the first electrical current;
expanding the aggregate electrically conductive zone into a second
region, adjacent the first region of the subterranean formation,
with the first electrical current, wherein the expanding creates a
second generation in situ resistive heating element within the
second region; transmitting a second electrical current in the
subterranean formation between a second electrode pair in
electrical contact with the second generation in situ resistive
heating element; powering the second generation in situ resistive
heating element with the second electrical current; and generating
heat with the second generation in situ resistive heating element
within the second region, wherein at least one electrode of the
second electrode pair extends within the second region.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority benefit of U.S.
Provisional Patent Application 61/901,234 filed Nov. 7, 2013
entitled SYSTEMS AND METHODS FOR IN SITU RESISTIVE HEATING OF
ORGANIC MATTER IN A SUBTERRANEAN FORMATION, the entirety of which
is incorporated by reference herein.
FIELD
[0002] The present disclosure is directed generally to systems and
methods for in situ resistive heating of organic matter in a
subterranean formation, and more particularly to systems and
methods for controlling the growth of in situ resistive heating
elements in the subterranean formation.
BACKGROUND
[0003] Certain subterranean formations may include organic matter,
such as shale oil, bitumen, and/or kerogen, which have material and
chemical properties that may complicate production of fluid
hydrocarbons from the subterranean formation. For example, the
organic matter may not flow at a rate sufficient for production.
Moreover, the organic matter may not include sufficient quantities
of desired chemical compositions (typically smaller hydrocarbons).
Hence, recovery of useful hydrocarbons from such subterranean
formations may be uneconomical or impractical.
[0004] Generally, organic matter is subject to decompose upon
exposure to heat over a period of time, via a process called
pyrolysis. Upon pyrolysis, organic matter, such as kerogen, may
decompose chemically to produce hydrocarbon oil, hydrocarbon gas,
and carbonaceous residue (the residue may be referred to generally
as coke). Coke formed by pyrolysis typically has a richer carbon
content than the source organic matter from which it was formed.
Small amounts of water also may be generated via the pyrolysis
reaction. The oil, gas, and water fluids may become mobile within
the rock or other subterranean matrix, while the residue coke
remains essentially immobile.
[0005] One method of heating and causing pyrolysis includes using
electrically resistive heaters, such as wellbore heaters, placed
within the subterranean formation. However, electrically resistive
heaters have a limited heating range. Though heating may occur by
radiation and/or conduction to heat materials far from the well, to
do so, a heater typically will heat the region near the well to
very high temperatures for very long times. In essence,
conventional methods for heating regions of a subterranean
formation far from a well may involve overheating the nearby
material in an attempt to heat the distant material. Such uneven
application of heat may result in suboptimal production from the
subterranean formation. Additionally, using wellbore heaters in a
dense array to mitigate the limited heating distance may be
cumbersome and expensive. Thus, there exists a need for more
economical and efficient heating of subterranean organic matter to
pyrolyze the organic matter.
SUMMARY
[0006] The present disclosure provides systems and methods for in
situ resistive heating of organic matter in a subterranean
formation to enhance hydrocarbon production.
[0007] A method for pyrolyzing organic matter in a subterranean
formation may comprise powering a first generation in situ
resistive heating element within an aggregate electrically
conductive zone at least partially in a first region of the
subterranean formation by transmitting an electrical current
between a first electrode pair in electrical contact with the first
generation in situ resistive heating element to pyrolyze a second
region of the subterranean formation, adjacent the first region, to
expand the aggregate electrically conductive zone into the second
region, wherein the expanding creates a second generation in situ
resistive heating element within the second region and powering the
second generation in situ resistive heating element by transmitting
an electrical current between a second electrode pair in electrical
contact with the second generation in situ resistive heating
element to generate heat with the second generation in situ
resistive heating element within the second region, wherein at
least one electrode of the second electrode pair extends within the
second region.
[0008] A method for pyrolyzing organic matter in a subterranean
formation may comprise transmitting a first electrical current in
the subterranean formation between a first electrode pair in
electrical contact with a first generation in situ resistive
heating element, powering a first generation in situ resistive
heating element, within an aggregate electrically conductive zone
at least partially in a first region of the subterranean formation,
with the first electrical current, and expanding the aggregate
electrically conductive zone into a second region, adjacent the
first region of the subterranean formation, with the first
electrical current. The expanding may create a second generation in
situ resistive heating element within the second region. The method
further may comprise transmitting a second electrical current in
the subterranean formation between a second electrode pair in
electrical contact with the second generation in situ resistive
heating element, powering the second generation in situ resistive
heating element with the second electrical current, and generating
heat with the second generation in situ resistive heating element
within the second region, wherein at least one electrode of the
second electrode pair extends within the second region.
[0009] The foregoing has broadly outlined the features of the
present disclosure so that the detailed description that follows
may be better understood. Additional features will also be
described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] These and other features, aspects and advantages of the
disclosure will become apparent from the following description,
appending claims and the accompanying drawings, which are briefly
described below.
[0011] FIG. 1 is a schematic view of a subterranean formation with
electrodes.
[0012] FIG. 2 is a schematic view of the subterranean formation of
FIG. 1 after powering a first generation in situ resistive heating
element.
[0013] FIG. 3 is a schematic view of the subterranean formation of
FIG. 2 identifying at least one second region.
[0014] FIG. 4 is a schematic view of the subterranean formation of
FIG. 3 after powering a second generation in situ resistive heating
element.
[0015] FIG. 5 is a schematic view of the subterranean formation of
FIG. 4 identifying at least one third region.
[0016] FIG. 6 is a flowchart depicting methods for in situ
resistive heating of organic matter in a subterranean
formation.
[0017] FIG. 7 is a schematic view of an arrangement of electrodes
within a subterranean formation.
[0018] FIG. 8 is a schematic view of an arrangement of electrodes
within a subterranean formation.
[0019] FIG. 9 is a schematic view of an arrangement of electrodes
within a subterranean formation.
[0020] FIG. 10 is a schematic view of an arrangement of electrodes
within a subterranean formation.
[0021] FIG. 11 is a schematic cross-sectional view of a system for
in situ resistive heating of organic matter in a subterranean
formation.
[0022] It should be noted that the figures are merely examples and
no limitations on the scope of the present disclosure are intended
thereby. Further, the figures are generally not drawn to scale, but
are drafted for purposes of convenience and clarity in illustrating
various aspects of the disclosure.
DETAILED DESCRIPTION
[0023] For the purpose of promoting an understanding of the
principles of the disclosure, reference will now be made to the
features illustrated in the drawings and specific language will be
used to describe the same. It will nevertheless be understood that
no limitation of the scope of the disclosure is thereby intended.
Any alterations and further modifications, and any further
applications of the principles of the disclosure as described
herein are contemplated as would normally occur to one skilled in
the art to which the disclosure relates. It will be apparent to
those skilled in the relevant art that some features that are not
relevant to the present disclosure may not be shown in the drawings
for the sake of clarity.
[0024] Thermal generation and stimulation techniques may be used to
produce subterranean hydrocarbons within, for example, subterranean
regions within a subterranean formation that contain and/or include
organic matter, and which may include large hydrocarbon molecules
(e.g., heavy oil, bitumen, and/or kerogen). Hydrocarbons may be
produced by heating for a sufficient period of time. In some
instances, it may be desirable to perform in situ upgrading of the
hydrocarbons, i.e., conversion of the organic matter to more mobile
forms (e.g., gas or liquid) and/or to more useful forms (e.g.,
smaller, energy-dense molecules). In situ upgrading may include
performing at least one of a shale oil retort process, a shale oil
heat treating process, a hydrogenation reaction, a thermal
dissolution process, and an in situ shale oil conversion process.
An shale oil retort process, which also may be referred to as
destructive distillation, involves heating oil shale in the absence
of oxygen until kerogen within the oil shale decomposes into liquid
and/or gaseous hydrocarbons. In situ upgrading via a hydrogenation
reaction includes reacting organic matter with molecular hydrogen
to reduce, or saturate, hydrocarbons within the organic matter. In
situ upgrading via a thermal dissolution process includes using
hydrogen donors and/or solvents to dissolve organic matter and to
crack kerogen and more complex hydrocarbons in the organic matter
into shorter hydrocarbons. Ultimately, the in situ upgrading may
result in liquid and/or gaseous hydrocarbons that may be extracted
from the subterranean formation.
[0025] When the in situ upgrading includes pyrolysis
(thermochemical decomposition), in addition to producing liquid
and/or gaseous hydrocarbons, a residue of carbonaceous coke may be
produced in the subterranean formation. Pyrolysis of organic matter
may produce at least one of liquid hydrocarbons, gaseous
hydrocarbons, shale oil, bitumen, pyrobitumen, bituminous coal, and
coke. For example, pyrolysis of kerogen may result in hydrocarbon
gas, shale oil, and/or coke. Generally, pyrolysis occurs at
elevated temperatures. For example, pyrolysis may occur at
temperatures of at least 250.degree. C., at least 350.degree. C.,
at least 450.degree. C., at least 550.degree. C., at least
700.degree. C., at least 800.degree. C., at least 900.degree. C.,
and/or within a range that includes or is bounded by any of the
preceding examples of pyrolyzation temperatures. As additional
examples, it may be desirable not to overheat the region to be
pyrolyzed. Examples of pyrolyzation temperatures include
temperatures that are less than 1000.degree. C., less than
900.degree. C., less than 800.degree. C., less than 700.degree. C.,
less than 550.degree. C., less than 450.degree. C., less than
350.degree. C., less than 270.degree. C., and/or within a range
that includes or is bounded by any of the preceding examples of
pyrolyzation temperatures.
[0026] Bulk rock in a subterranean formation 28 may contain organic
matter. Bulk rock generally has a low electrical conductivity
(equivalently, a high electrical resistivity), typically on the
order of 10.sup.-7-10.sup.-4 S/m (a resistivity of about
10.sup.4-10.sup.7 .OMEGA.m). For example, the average electrical
conductivity within a subterranean formation, or a region within
the subterranean formation, may be less than 10.sup.-3 S/m, less
than 10.sup.-4 S/m, less than 10.sup.-5 S/m, less than 10.sup.-6
S/m, and/or within a range that includes or is bounded by any of
the preceding examples of average electrical conductivities. Most
types of organic matter found in subterranean formations have
similarly low conductivities. However, the residual coke resulting
from pyrolysis is relatively enriched in carbon and has a
relatively higher electrical conductivity. For example, Green River
oil shale (a rock including kerogen) may have an average electrical
conductivity in ambient conditions of about 10.sup.-7-10.sup.-6
S/m. As the Green River oil shale is heated to between about
300.degree. C. and about 600.degree. C., the average electrical
conductivity may rise to greater than 10.sup.-5 S/m, greater than 1
S/m, greater than 100 S/m, greater than 1,000 S/m, even greater
than 10,000 S/m, or within a range that includes or is bounded by
any of the preceding examples of electrical conductivities. This
increased electrical conductivity may remain even after the rock
returns to lower temperatures.
[0027] Continued heating (increasing temperature and/or longer
duration) may not result in further increases of the electrical
conductivity of a subterranean region. Other components of the
subterranean formation, e.g., carbonate minerals such as dolomite
and calcite, may decompose at a temperature similar to useful
pyrolysis temperatures. For example, dolomite may decompose at
about 550.degree. C., while calcite may decompose at about
700.degree. C. Decomposition of carbonate minerals generally
results in carbon dioxide, which may reduce the electrical
conductivity of subterranean regions neighboring the decomposition.
For example, decomposition may result in an average electrical
conductivity in the subterranean regions of less than 0.1 S/m, less
than 0.01 S/m, less than 10.sup.-3 S/m, less than 10.sup.-4 S/m,
less than 10.sup.-5 S/m, and/or within a range that includes or is
bounded by any of the preceding examples of average electrical
conductivities.
[0028] If a pyrolyzed subterranean region has sufficient electrical
conductivity, generally greater than about 10.sup.-5 S/m, the
region may be described as an electrically conductive zone. An
electrically conductive zone may include bitumen, pyrobitumen,
bituminous coal, and/or coke produced by pyrolysis. An electrically
conductive zone is a region within a subterranean formation that
has an electrical conductivity greater than, typically
significantly greater than, the unaffected bulk rock of the
subterranean formation. For example, the average electrical
conductivity of an electrically conductive zone may be at least
10.sup.-5 S/m, at least 10.sup.-4 S/m, at least 10.sup.-3 S/m, at
least 0.01 S/m, at least 0.1 S/m, at least 1 S/m, at least 10 S/m,
at least 100 S/m, at least 300 S/m, at least 1,000 S/m, at least
3,000 S/m, at least 10,000 S/m, and/or within a range that includes
or is bounded by any of the preceding examples of average
electrical conductivities.
[0029] The residual coke after pyrolysis may form an electrically
conductive zone that may be used to conduct electricity and act as
an in situ resistive heating element for continued upgrading of the
hydrocarbons. An in situ resistive heating element may include an
electrically conductive zone that has a conductivity sufficient to
cause ohmic losses, and thus resistive heating, when electrically
powered by at least two electrodes. For example, the average
electrical conductivity of an in situ resistive heating element 40
may be at least 10.sup.-5 S/m, at least 10.sup.-4 S/m, at least
10.sup.-3 S/m, at least 0.01 S/m, at least 0.1 S/m, at least 1 S/m,
at least 10 S/m, at least 100 S/m, at least 300 S/m, at least 1,000
S/m, at least 3,000 S/m, and/or at least 10,000 S/m, and/or within
a range that includes or is bounded by any of the preceding
examples of average electrical conductivities. An in situ resistive
heating element 40 that can expand, such as due to the heat
produced by the resistive heating element, also may be referred to
as a self-amplifying heating element.
[0030] When electrical power is applied to the in situ resistive
heating element, resistive heating heats the heating element.
Neighboring (i.e., adjacent, contiguous, and/or abutting) regions
of the subterranean formation may be heated primarily by conduction
of the heat from the in situ resistive heating element. The heating
of the subterranean formation, including the organic matter, may
cause pyrolysis and consequent increase in conductivity of the
subterranean region. Under voltage-limited conditions (e.g.,
approximately constant voltage conditions), an increase in
conductivity (decrease in resistivity) causes increased resistive
heating. Hence, as electrical power is applied to the in situ
resistive heating element, the heating of neighboring regions
creates more electrically conductive zones. These zones may become
a part of a growing, or expanding, electrically conductive zone and
in situ resistive heating element, provided that sufficient current
can continue to be supplied to the (expanding) in situ resistive
heating element. Alternatively expressed, as the subterranean
regions adjacent to the actively heated in situ resistive heating
element become progressively more conductive, the electrical
current path begins to spread to these newly conductive regions and
thereby expands the extent of the in situ resistive heating
element.
[0031] For subterranean regions that contain interfering components
such as carbonate minerals, the pyrolysis and the expansion of the
in situ resistive heating element may be accompanied by a local
decrease in electrical conductivity (e.g., resulting from the
decomposition of carbonate in the carbonate minerals and/or other
interfering components). Generally, decomposition of any such
interfering components occurs in the hottest part of the expanding
in situ resistive heating element, e.g., the central volume, or
core, of the heating element. These two effects, an expanding
exterior of the in situ resistive heating element and an expanding
low conductivity core, may combine to form a shell of rock that is
actively heating. A shell-shaped in situ resistive heating element
may be beneficial because the active heating would be concentrated
in the shell, generally a zone near unpyrolyzed regions of the
subterranean formation. The central volume, which was already
pyrolyzed, may have little to no further active heating. Aside from
concentrating the heating on a more useful (such as a partially or
to-be-pyrolyzed) subterranean region, the shell configuration also
may reduce the total electrical power requirements to power the
shell-shaped in situ resistive heating element as compared to a
full-volume in situ resistive heating element.
[0032] FIGS. 1-5 are schematic views of a subterranean formation 28
including organic matter. These figures show various electrodes 50
within the subterranean formation 28 along with in situ resistive
heating elements 40 at various points in time, such as before,
during, and/or after performance of methods 10. FIG. 6 is a
flowchart illustrating methods 10 for pyrolyzing organic matter in
a subterranean formation 28, namely, by in situ resistive heating
of the organic matter within the subterranean formation. FIGS. 7-10
are schematic views of various electrode arrangements. The various
electrode arrangements illustrate some of the options for
configuring and/or placing electrodes 50 within a subterranean
formation 28. FIG. 11 is a schematic cross-sectional view of a
system for pyrolyzing organic matter within a subterranean
formation 28.
[0033] FIGS. 1-5 and 7-11 provide examples of systems and
configurations that contain an in situ resistive heating element
40, which may be a self-amplifying in situ heating element, and/or
which are formed via methods 10. Elements that serve a similar, or
at least substantially similar, purpose are labeled with like
numbers in each of FIGS. 1-5 and 7-11. Each of these elements may
not be discussed in detail with reference to each of FIGS. 1-5 and
7-11. Similarly, all elements may not be labeled in each of FIGS.
1-5 and 7-11, but reference numerals associated therewith may be
used for consistency. Elements that are discussed with reference to
one or more of FIGS. 1-5 and 7-11 may be included in and/or used
with any of FIGS. 1-5 and 7-11 without departing from the scope of
the present disclosure. In general, elements that are likely to be
included are illustrated in solid lines, while elements that are
optional are illustrated in dashed lines. However, elements that
are shown in solid lines may not be essential. Thus, an element
shown in solid lines may be omitted without departing from the
scope of the present disclosure.
[0034] Generally, FIGS. 1-5 and 7-11 schematically illustrate the
control and growth of in situ resistive heating elements 40 to
pyrolyze organic matter within a subterranean formation 28, such as
via methods 10. As viewed in FIG. 1, a subterranean formation 28
may include a first region 41 which may enclose a first generation
in situ resistive heating element 44. A first generation in situ
resistive heating element 44 is an electrically conductive zone
within the first region 41. First region 41 is in electrical
contact with at least two electrodes 50, which may be referred to
as a first electrode pair 51. The subterranean formation 28 also
may include one or more electrodes 50 that are not in electrical
contact with the first generation in situ resistive heating element
44, at least not at the time point illustrated in FIG. 1.
[0035] FIG. 2 illustrates the subterranean formation 28 and
electrode 50 arrangement of FIG. 1 after electrically powering the
first generation in situ resistive heating element 44 to heat a
portion of the subterranean formation 28 that includes the first
generation in situ resistive heating element 44. The first
generation in situ resistive heating element 44 may be powered via
the first electrode pair 51. The heating may cause pyrolysis of
organic matter contained within the heated portion and consequently
may increase the average electrical conductivity of the heated
portion. In FIG. 2, the powering has resulted in an expansion of
the electrically conductive zone, which may be referred to as an
aggregate electrically conductive zone 48. Initially (in FIG. 1),
the electrically conductive zone was coextensive with the first
generation in situ resistive heating element 44. After powering (as
viewed in FIG. 2), the aggregate electrically conductive zone 48
may be larger, i.e., expanded.
[0036] The aggregate electrically conductive zone 48 may expand
sufficiently to electrically contact one or more electrodes 50 that
were not initially contacted by the in situ resistive heating
element 40, i.e., prior to the expansion of the aggregate
electrically conductive zone 48. Hence, the expansion of the
aggregate electrically conductive zone 48 results in the electrical
contact of a pair of electrodes 50 that is distinct from the first
electrode pair 51.
[0037] FIG. 3 illustrates one or more second regions 42 that
intersect the (expanded) aggregate electrically conductive zone 48.
Second regions 42 are generally subterranean regions, adjacent to
the first region 41. Each second region 42 encloses a portion of
the aggregate electrically conductive zone 48 but is
distinct/separate from first region 41 and, when present, other
second region(s) 42. Second region 42 may intersect and/or adjoin
the first region 41. Second region 42 may be spaced apart from the
first region 41 and/or at least one other second region 42. Each
second region 42 may include a second generation in situ resistive
heating element 45, a portion of the aggregate electrically
conductive zone 48 within the second region 42 that is electrically
contacted by a second electrode pair 52. Each second electrode pair
52 may be distinct from the first electrode pair 51, as well as
other second electrode pairs 52.
[0038] Once electrical contact between the second electrode pair 52
and the aggregate electrically conductive zone 48 is established,
forming a second generation in situ resistive heating element 45,
the second generation in situ resistive heating element 45 may be
used to heat the second region 42 and neighboring regions of the
subterranean formation 28. Electrically powering the second
generation in situ resistive heating element 45 may heat a portion
of the subterranean formation 28 that includes the second
generation in situ resistive heating element 45. The second
generation in situ resistive heating element 45 may be powered via
the second electrode pair 52. The heating may cause pyrolysis of
organic matter contained within the heated portion. The heating may
increase the average electrical conductivity of the heated portion.
In FIG. 4, the powering has resulted in further expansion of the
electrically conductive zone, resulting in an aggregate
electrically conductive zone 48 that is larger than the aggregate
electrically conductive zone 48 of FIG. 3.
[0039] FIG. 4 illustrates the (further expanded) aggregate
electrically conductive zone 48 after it has expanded sufficiently
to electrically contact one or more electrodes 50 that were not
contacted by the aggregate electrically conductive zone 48 prior to
the expansion. Hence, the expansion of the aggregate electrically
conductive zone 48 results in the electrical contact of a pair of
electrodes 50 that is distinct from the second electrode pair
52.
[0040] FIG. 4 also illustrates continued expansion of the aggregate
electrically conductive zone 48 as a result of continued powering
of the first generation in situ resistive heating element 44. Any
pair of electrodes 50 within the aggregate electrically conductive
zone 48, whether in contact with the first region 41 or a second
region 42, may be operated independently to electrically power one
or more of the first generation in situ resistive heating element
44 and the second generation in situ resistive heating element(s)
45.
[0041] FIG. 5 illustrates one or more third regions 43 that
intersect the (further expanded) aggregate electrically conductive
zone 48. Third regions 43 are generally subterranean regions,
adjacent to a second region 42. Each third region 43 encloses a
portion of the aggregate electrically conductive zone 48 but is
distinct/separate from first region 41, second region(s) 42, and
(when present) other third region(s) 43. Third region 43 may
intersect and/or adjoin at least one of the first region 41 and the
second region(s) 42. Third region 43 may be spaced apart from at
least one of the first region 41, the second region(s) 42, and/or
at least one other third region 43. Each third region 43 may
include a third generation in situ resistive heating element 46, a
portion of the aggregate electrically conductive zone 48 within the
third region 43 that is electrically contacted by a third electrode
pair 53. Each third electrode pair 53 may be distinct from the
first electrode pair 51, second pairs of electrodes 52, and other
third electrode pairs 53.
[0042] Once electrical contact between the third electrode pair 53
and the aggregate electrically conductive zone 48 is established,
forming a third generation in situ resistive heating element 46,
the third generation in situ resistive heating element 46 may be
used to heat the third zone 43. Electrically powering the third
generation in situ resistive heating element 46 may heat a portion
of the subterranean formation 28 including the third generation in
situ resistive heating element 46. The third generation in situ
resistive heating element 46 may be powered via the third electrode
pair 53. The heating may cause pyrolysis of organic matter
contained within the heated portion and consequently may increase
the average electrical conductivity of the portion. The powering
may result in further expansion of the aggregate electrically
conductive zone 48, potentially contacting further electrodes
50.
[0043] A subterranean formation 28 may be any suitable structure
that includes and/or contains organic matter (FIGS. 1-5). For
example, the subterranean formation 28 may contain at least one of
oil shale, shale gas, coal, tar sands, organic-rich rock, kerogen,
and bitumen. The subterranean formation 28 may be a geological
formation, a geological member, a geological bed, a rock stratum, a
lithostratigraphic unit, a chemostratigraphic unit, and/or a
biostratigraphic unit, or groups thereof. The subterranean
formation 28 may have a thickness less than 2000 m, less than 1500
m, less than 1000 m, less than 500 m, less than 250 m, less than
100 m, less than 80 m, less than 60 m, less than 40 m, less than 30
m, less than 20 m, and/or less than 10 m. The subterranean
formation 28 may have a thickness that is greater than 5 m, greater
than 10 m, greater than 20 m, greater than 30 m, greater than 40 m,
greater than 60 m, greater than 80 m, greater than 100 m, greater
than 250 m, greater than 500 m, greater than 1000 m, and/or greater
than 1500 m. Additionally, the subterranean formation may have a
thickness of any of the preceding examples of maximum and minimum
thicknesses and/or a thickness in a range that is bounded by any of
the preceding examples of maximum and minimum values.
[0044] Electrodes 50 may be electrically conductive elements,
typically including metal and/or carbon, that may be in electrical
contact with a portion of the subterranean formation 28. Electrical
contact includes contact sufficient to transmit electrical power,
including AC and DC power. Electrical contact may be established
between two elements by direct contact between the elements. Two
elements may be in electrical contact when indirectly linked by
intervening elements, provided that the intervening elements are at
least as conductive as the least conductive of the two connected
elements, i.e., the intervening elements do not dominate current
flow between the elements in contact. The conductance of an element
is proportional to its conductivity and its cross sectional area,
and inversely proportional to its current path length. Hence, small
elements with low conductivities may have high conductance.
[0045] Whether a subterranean region is poorly electrically
conductive (e.g., having an electrical conductivity below 10.sup.-4
S/m) or not poorly electrically conductive (e.g., having an
electrical conductivity above 10.sup.-4 S/m and alternatively
referred to as highly electrically conductive), an electrode 50 may
be in electrical contact with the subterranean region by direct
contact between the electrode 50 and the region and/or by indirect
contact via suitable conductive intervening elements. For example,
remnants from drilling fluid (mud), though typically not highly
electrically conductive (typical conductivities range from
10.sup.-5 S/m to 1 S/m), may be sufficiently electrically
conductive to provide suitable electrical contact between an
electrode 50 and a subterranean region. Where an electrode 50 is
situated within a wellbore, the electrode may be engaged directly
against the wellbore, or an electrically conductive portion of the
casing of the wellbore, thus causing electrical contact between the
electrode and the subterranean region surrounding the wellbore. An
electrode 50 may be in electrical contact with a subterranean
region through subterranean spaces (e.g., natural and/or manmade
fractures; voids created by hydrocarbon production) filled with
electrically conductive materials (e.g., graphite, coke, and/or
metal particles).
[0046] Electrodes 50 may be operated in spaced-apart pairs (two or
more electrodes), for example, a first electrode pair 51, a second
electrode pair 52, a third electrode pair 53, etc. A pair of
electrodes 50 may be used to electrically power an in situ
resistive heating element in electrical contact with each of the
electrodes 50 of the pair. Electrical power may be transmitted
between more than two electrodes 50. Two electrodes 50 may be held
at the same electrical potential while a third electrode 50 is held
at a different potential. Two or more electrodes may transmit AC
power with each electrode transmitting a different phase of the
power signal. Each of the first electrode pair 51, the second
electrode pair 52, and the third electrode pair 53 may be distinct,
meaning each pair includes an electrode not shared with another
pair. Electrode pairs (the first electrode pair 51, the second
electrode pair 52, and the third electrode pair 53) may include at
least one shared electrode 50, provided that less than all
electrodes 50 are shared with one other electrode pair.
[0047] Electrodes 50 may be contained at least partially within an
electrode well 60 in the subterranean formation 28. Electrodes 50
may be placed at least partially within an electrode well 60.
Electrode wells 60 may include one or more electrodes 50. In the
case of multiple electrodes 50 contained within one electrode well
60, the electrodes 50 may be spaced apart and insulated from each
other. One electrode well 60 may be placed for each electrode 50,
for each electrode of the first electrode pair 51, for each
electrode of the second electrode pair 52, and/or for each
electrode of the third electrode pair 53. An electrode 50 may
extend outside of an electrode well 60 and into the subterranean
formation 28, for example, through a natural and/or manmade
fracture.
[0048] An electrode well 60 may include an end portion that
contains at least one electrode 50. End portions of electrode wells
60 may have a specific orientation relative to the subterranean
formation 28, regions of the subterranean formation 28, and/or
other electrode wells 60. For example, the end portion of one of
the electrode wells 60 may be co-linear with, and spaced apart
from, the end portion of another of the electrode wells 60. The end
portion of one of the electrode wells 60 may be at least one of
substantially parallel, parallel, substantially co-planar, and
co-planar to the end portion of another of the electrode wells 60.
The end portion of one of the electrode wells 60 may converge
towards or diverge away from the end portion of another of the
electrode wells 60. Where at least one of the subterranean
formation 28, a region of the subterranean formation 28, and an in
situ resistive heating element 40 is elongate with an elongate
direction, the end portion of one of the electrode wells 60 may be
at least one of substantially parallel, parallel, oblique,
substantially perpendicular, and perpendicular to the elongate
direction.
[0049] Electrode wells 60 may include a portion, optionally
including the end portion, that may be at least one of horizontal,
substantially horizontal, inclined, vertical, and substantially
vertical. Electrode wells 60 also may include a differently
oriented portion, which may be at least one of horizontal,
substantially horizontal, inclined, vertical, and substantially
vertical.
[0050] A subterranean formation 28 may include a production well
64, from which hydrocarbons and/or other fluids are extracted or
otherwise removed from the subterranean formation 28. A production
well 64 may extract mobile hydrocarbons produced in the
subterranean formation 28 by in situ pyrolysis. A production well
64 may be placed in fluidic contact with at least one of the
subterranean formation 28, the first region 41, the first
generation in situ resistive heating element 44, the second
region(s) 42, the second generation in situ resistive heating
element(s) 45, the third region(s) 43, and the third generation in
situ resistive heating element(s) 46. A production well 64 may be
placed prior to the generation of at least one of the in situ
resistive heating elements 40. When present, an electrode well 60
may also serve as a production well 64, in which case the electrode
well 60 may extract mobile components from the subterranean
formation 28.
[0051] FIG. 6 illustrates methods 10, which describe the process of
iteratively expanding an aggregate electrically conductive zone 48
into electrical contact with one or more electrodes 50 that were
not previously contacted by the aggregate electrically conductive
zone 48 (i.e., prior to the expansion of the aggregate electrically
conductive zone 48). Methods 10 may comprise a first generation
powering 11 of a first generation in situ resistive heating element
44 to expand an aggregate electrically conductive zone 48. Methods
may include a second generation powering 12 to heat a second
generation in situ resistive heating element 45 resulting from the
expanding aggregate electrically conductive zone 48.
[0052] First generation powering 11 may include transmitting an
electrical current between a first electrode pair 51 in electrical
contact with the first generation in situ resistive heating element
44. First generation powering 11 may cause resistive heating within
the first generation in situ resistive heating element 44 and
consequently pyrolysis within the first region 41 and neighboring
regions within the subterranean formation 28. For example, one or
more second regions 42, each adjacent the first region 41, may be
heated and pyrolyzed by the first generation powering 11.
[0053] Pyrolyzing a second region 42 by the first generation
powering 11 may include increasing an average electrical
conductivity of the second region 42 sufficiently to expand the
aggregate electrically conductive zone 48 into the second region
42. The expansion of the aggregate electrically conductive zone 48
may cause electrical contact with an electrode 50 that extends
within the second region 42 and/or that is outside the first region
41. The electrode 50 may extend within the second region 42 and/or
be outside the first region 41 before, during, or after the
expansion of the aggregate electrically conductive zone 48.
[0054] Once the first generation powering 11 establishes electrical
contact between the aggregate electrically conductive zone 48 and
at least one electrode 50 that was not in prior contact, the second
generation powering 12 may begin. Second generation powering 12,
analogous to first generation powering 11, may include electrically
powering a second generation in situ resistive heating element 45
using a second electrode pair 52, by transmitting an electrical
current between the electrodes 50. Second generation powering 12
may cause resistive heating within the second generation in situ
resistive heating element 45 and consequently pyrolysis within the
second region 42 and neighboring regions within the subterranean
formation 28. For example, one or more third regions 43, adjacent
at least one second region 42, may be heated and pyrolyzed by the
second generation powering 12.
[0055] Pyrolyzing a third region 43 by the second generation
powering 12 may include increasing an average electrical
conductivity of the third region 43 sufficiently to expand the
aggregate electrically conductive zone 48 into the third region 43.
The expansion of the aggregate electrically conductive zone 48 may
cause electrical contact with an electrode 50 that extends within
the third region 43 and/or that is outside the first region 41 and
the second region(s) 42. The electrode 50 may extend within the
third region 43 and/or be outside the first region 41 and the
second region(s) 42 before, during, or after the expansion of the
aggregate electrically conductive zone 48.
[0056] Once the second generation powering 12 establishes
electrical contact between the aggregate electrically conductive
zone 48 and at least one electrode 50 that was not in prior
contact, a third generation powering 13 may begin. Third generation
powering 13, analogous to first generation powering 11 and second
generation powering 12, may include electrically powering a third
generation in situ resistive heating element 46 using a third
electrode pair 53, by transmitting an electrical current between
the electrodes 50. Third generation powering 13 may cause resistive
heating within the third generation in situ resistive heating
element 46. Third generation powering 13 may cause pyrolysis within
the third region 43. Third generating powering 13 may cause
pyrolysis within neighboring regions within the subterranean
formation 28. For example, one or more fourth regions, adjacent at
least one third region 43, may be heated and pyrolyzed by the third
generation powering 13.
[0057] The iterative cycle of powering an in situ resistive heating
element 40, thereby expanding the aggregate electrically conductive
zone 48, and powering another in situ resistive heating element 40
within the expanded aggregate electrically conductive zone 48 may
continue to a fourth generation, a fifth generation, etc., as
indicated by the continuation lines at the bottom of FIG. 6.
[0058] Once electrical contact is established with an in situ
resistive heating element 40, powering of that in situ resistive
heating element 40 may begin regardless of whether the powering
that generated the electrical contact continues. Electrical
powering of each in situ resistive heating element 40 may be
independent and/or may be independently controlled.
[0059] First generation powering 11, second generation powering 12,
third generation powering 13, etc. may occur at least partially
concurrently and/or at least partially sequentially. As examples,
second generation powering 12 may sequentially follow the
completion of first generation powering 11. Third generation
powering may sequentially follow the completion of second
generation powering 12. First generation powering 11 may cease
before, during, or after either of second generation powering 12
and third generation powering 13. Second generation powering 12 may
include at least partially sequentially and/or at least partially
concurrently powering each of the second generation in situ
resistive heating element(s) 45. Third generation powering 13 may
include at least partially sequentially and/or at least partially
concurrently powering each of the third generation in situ
resistive heating element(s) 46.
[0060] Concurrently powering may include at least partially
concurrently performing the first generation powering 11, the
second generation powering 12, and/or the third generation powering
13; or at least partially concurrently powering two or more second
generation in situ resistive heating element(s) 45 and/or third
generation in situ resistive heating element(s) 46. Concurrently
powering may include partitioning electrical power between the
active (powered) in situ resistive heating elements 40. As
examples, beginning the second generation powering 12 may include
reducing power to the first generation in situ resistive heating
element 44 and/or ceasing the first generation powering 11. Second
generation powering 12 may include powering two second generation
in situ resistive heating element(s) 46 with unequal electrical
powers. Third generation powering 13 may include reducing power to
one or more second generation in situ resistive heating element(s)
45 and/or the first generation in situ resistive heating element
44.
[0061] Further, although not required, independent control of in
situ resistive heating elements 40 effectively may be utilized to
split and/or partition the aggregate electrically conductive zone
48 into several independent active in situ resistive heating
elements 40. These independently-controlled in situ resistive
heating elements 40 may remain in electrical contact with each
other, or, because of changing conductivity due to heating (and/or
overheating), may not be in electrical contact with at least one
other in situ resistive heating element 40.
[0062] First generation powering 11, second generation powering 12,
and/or third generation powering 13 may include transmitting
electrical current for a suitable time to pyrolyze organic matter
within the corresponding region of the subterranean formation 28
and to expand the in situ resistive heating element 40 into a
produced electrically conductive zone in an adjacent region of the
subterranean formation. For example, first generation powering 11,
second generation powering 12, and/or third generation powering 13
each independently may include transmitting electrical current for
at least one day, at least one week, at least two weeks, at least
three weeks, at least one month, at least two months, at least
three months, at least four months, at least five months, at least
six months, at least one year, at least two years, at least three
years, at least four years, or within a range that includes or is
bounded by any of the preceding examples of time.
[0063] Methods 10 may comprise pyrolyzing 14 at least a portion of
the first region 41, for example, to generate an aggregate
electrically conductive zone 48 and/or a first generation in situ
resistive heating element 44 within the first region 41. The
pyrolyzing 14 may include heating the first region 41. Heating may
be accomplished, for example, using a conventional heating element
58 or initiating combustion within the subterranean formation 28.
For example, a conventional heating element 58 may be or include a
wellbore heater and/or a granular resistive heater (a heater formed
with resistive materials placed within a wellbore or the
subterranean formation 28). Pyrolyzing 14 the first region 41 may
include transmitting electrical current between electrodes 50
(e.g., a first electrode pair 51) in electrical contact with the
first region 41 (e.g., by electrolinking). Pyrolyzing 14 the first
region 41 may include transmitting electrical current between
electrodes 50 (e.g., a first electrode pair 51) in electrical
contact with the first generation in situ resistive heating element
44, once the first generation in situ resistive heating element 44
begins to form. Pyrolyzing 14 the first region 41 may include
generating heat with the first generation in situ resistive heating
element 44 to heat the first region 41. Pyrolyzing the first region
41 may include increasing an average electrical conductivity of the
first region 41.
[0064] Methods 10 may comprise determining 15 a desired geometry of
an in situ resistive heating element 40 and/or the aggregate
electrically conductive zone 48. The determining 15 may occur prior
to first generation powering 11, the second generation powering 12,
and/or the third generation powering 13. The determining 15 may be
at least partially based on data relating to at least one of the
subterranean formation 28 and the organic matter in the
subterranean formation 28. For example, the determining 15 may be
based upon geophysical data relating to a shape, an extent, a
volume, a composition, a density, a porosity, a permeability,
and/or an electrical conductivity of the subterranean formation 28
and/or a region of the subterranean formation 28. Determining 15
may include estimating, modeling, forecasting and/or measuring the
heating, pyrolyzing, electrical conductivity, permeability, and/or
hydrocarbon production of the subterranean formation 28 and/or a
region of the subterranean formation 28.
[0065] Methods 10 may comprise placing 16 electrodes 50 into
electrical contact with at least a portion of the subterranean
formation 28. As examples, placing 16 may include placing the first
electrode pair 51 into electrical contact with the first generation
in situ resistive heating element 44 and/or the first region 41.
Placing 16 may include placing at least one of the second electrode
pair 52 into electrical contact with the second region 42. Further,
placing 16 may include placing at least one of the second electrode
pair 52 within the subterranean formation 28 outside of the first
generation in situ resistive heating element 44. Electrodes 50 may
be placed in anticipation of growth of the aggregate electrically
conductive zone 48. Electrodes 50 may be placed to guide and/or
direct the aggregate electrically conductive zone 48 toward
subterranean regions of potentially higher productivity and/or of
higher organic matter content.
[0066] Placing 16 may occur at any time. Placing 16 an electrode 50
may be more convenient and/or practical before heating the portion
of the subterranean formation 28 that will neighbor (i.e., be
adjacent to), much less include, the placed electrode 50. The first
electrode pair 51 may be placed 16 into electrical contact with the
first region 41 prior to the creation of the first generation in
situ resistive heating element 44. The second electrode pair 52 may
be placed into electrical contact with the second region 42 prior
to the creation of the first generation in situ resistive heating
element 44 and/or the second generation in situ resistive heating
element 45. The second electrode pair 52 may be placed within the
subterranean formation 28 outside of the first region 41 prior to
the creation of the first generation in situ resistive heating
element 44 and/or the second generation in situ resistive heating
element 45. Placing 16 may occur after determining 15 a desired
geometry for an in situ resistive heating element 40 and/or the
aggregate electrically conductive zone 48.
[0067] Placing 16 electrodes 50 into electrical contact with at
least a portion of the subterranean formation 28 may include
placing an electrode well 60 that contains at least one electrode
50. Placing 16 also may include placing an electrode 50 into an
electrode well 60. Placing electrode wells 60 may occur at any time
prior to electrical contact of the electrodes 50 with the
subterranean formation 28. In particular, similar to the placing 16
of electrodes 50, placing an electrode well 60 may be more
convenient and/or practical before heating the portion of the
subterranean formation 28 that will neighbor and/or include the
placed electrode well 60. For example, drilling a well may be
difficult at temperatures above the boiling point of drilling fluid
components. An electrode well 60 may be placed into the
subterranean formation 28 prior to the creation of the first
generation in situ resistive heating element 44 and/or the second
generation in situ resistive heating element 45. An electrode well
60 may be placed within the subterranean formation 28 outside of
the first region 41 prior to the creation of the first generation
in situ resistive heating element 44 and/or the second generation
in situ resistive heating element 45. An electrode well 60 may be
placed within the subterranean formation 28 after the determining
15 a desired geometry.
[0068] Methods 10 may comprise regulating 17 the creation of an in
situ resistive heating element 40 and/or pyrolyzation of a
subterranean region. Regulating 17 may include monitoring a
parameter before, during, and/or after powering (e.g., first
generation powering 11, second generation powering 12, third
generation powering 13, etc.). Regulating 17 may include monitoring
a parameter before, during, and/or after pyrolyzing. The monitored
parameter may relate to at least one of the subterranean formation
28 and the organic matter in the subterranean formation 28. As
examples, the monitored parameter may include geophysical data
relating to a shape, an extent, a volume, a composition, a density,
a porosity, a permeability, an electrical conductivity, an
electrical property, a temperature, and/or a pressure of the
subterranean formation 28 and/or a region of the subterranean
formation 28. The monitored parameter may relate to the production
of mobile components within the subterranean formation 28 (e.g.,
hydrocarbon production). The monitored parameter may relate to the
electrical power applied to at least a portion of the subterranean
formation 28. For example, the monitored parameter may include at
least one of the duration of applied electrical power, the
magnitude of electrical power applied, and the magnitude of
electrical current transmitted. The magnitude may include the
average value, the peak value, and/or the integrated total
value.
[0069] Regulating 17 may include adjusting subsequent powering
and/or pyrolyzing based upon a monitored parameter and/or based
upon a priori data relating to the subterranean formation 28. A
priori data may relate to estimates, models, and/or forecasts of
the heating, pyrolyzing, electrical conductivity, permeability,
and/or hydrocarbon production of the subterranean formation 28
and/or a region of the subterranean formation 28. Regulating 17 may
include adjusting subsequent powering and/or pyrolyzing when a
monitored parameter and/or a priori data are greater than, equal
to, or less than a predetermined threshold. The adjusting may
include starting, stopping, and/or continuing the powering of at
least one in situ resistive heating element 40. The adjusting may
include powering with an adjusted electrical power, electrical
current, electrical polarity, and/or electrical power phase.
[0070] Regulating 17 may include partitioning electrical power
among a plurality of in situ resistive heating elements 40. For
example, first generation powering 11, second generation powering
12, and/or third generation powering 13 may be regulated to control
the growth of the aggregate electrically conductive zone 48.
Partitioning the electrical power may include controlling at least
one of the duration of applied electrical power, the magnitude of
electrical power applied, and the magnitude of electrical current
transmitted. The magnitude may include the average value, the peak
value, and/or the integrated total value.
[0071] FIGS. 7-10 illustrate arrangements of electrodes 50 within a
subterranean formation 28 that may be suitable for systems 30
and/or for carrying out methods 10. Any of the electrodes 50
illustrated in FIGS. 7-10 may be substituted for any one or more
electrodes 50 illustrated in FIGS. 1-5 and 11. Moreover, though the
FIGS. 7-10 illustrate a first region 41 and a second region 42 (and
corresponding components), the electrode arrangements of FIGS. 7-10
are equally applicable to any subterranean region and/or any in
situ resistive heating element 40.
[0072] FIG. 7 illustrates a collinear, spaced-apart first electrode
pair 51. When an in situ resistive heating element 40 is
electrically powered, the in situ resistive heating element 40 may
heat and pyrolyze neighboring subterranean regions. The heating and
pyrolyzing may cause an aggregate electrically conductive zone 48
to expand along the elongated dimension of each of the electrodes
50. As the aggregate electrically conductive zone 48 expands, the
degree and/or extent of electrical contact between the aggregate
electrically conductive zone 48 and at least one of the electrodes
50 may increase. Electrodes 50 may be configured for extended
electrical contact when. Electrodes may be configured for extended
electrical contact when an electrode is contained within a porous
and/or perforated electrode well 60. Electrodes 50 at least
partially contained within a natural and/or manmade fracture within
the subterranean formation 28 may have extended electrical contact
with a portion of the subterranean formation 28.
[0073] FIG. 7 illustrates a structure that may be used to generate
an initial in situ resistive heating element 40 within the
subterranean formation 28. An electrode well 60, or generally the
subterranean formation 28, may contain a conventional heating
element 58, such as a wellbore heater. In FIG. 7, the conventional
heating element 58 is schematically depicted as being located in an
electrode well 60 within a horizontal portion of the well, although
conventional heating element 58 also may be located within a
vertical or other angularly oriented potion of the well. On either
side of the conventional heating element 58, within the same
electrode well 60, may be an electrode 50, such as one formed from
graphite, coke, and/or metal particles packed into the electrode
well 60. The conventional heating element 58 and the two electrodes
50 may have independent electrical connections to one or more
electrical power sources. Upon operation of the conventional
heating element 58, a first region 41 of the subterranean formation
28 may be heated and pyrolyzed to generate a first generation in
situ resistive heating element 44. Once the first generation in
situ resistive heating element 44 is electrically connected to the
first electrode pair 51, the first generation in situ resistive
heating element 44 may be electrically powered via the first
electrode pair 51.
[0074] FIG. 8 illustrates a first electrode pair 51 with a parallel
portion, each electrode 50 of the pair configured for extended
electrical contact. When an in situ resistive heating element 40 in
electrical contact with a parallel pair of electrodes 50 is
electrically powered, the in situ resistive heating element 40 may
heat and pyrolyze neighboring subterranean regions, causing an
aggregate electrically conductive zone 48 to expand along the
length of the parallel electrodes, generally perpendicular to the
shortest direction between the electrodes 50. As the aggregate
electrically conductive zone 48 expands, the degree and/or extent
of electrical contact between the aggregate electrically conductive
zone 48 and at least one of the electrodes 50 may increase.
[0075] FIG. 9 illustrates a first electrode pair 51 with a
diverging portion, each electrode 50 of the pair configured for
extended electrical contact. A portion of a pair of electrodes 50
may be considered diverging if the portion is not generally
parallel, e.g., the distance between the electrodes 50 at one end
is greater than the distance between the electrodes 50 at another
end. For example (as illustrated in FIG. 9), the distance between
the first electrode pair 51 within the first generation in situ
resistive heating element 44 may be greater than the distance
between the same electrodes 50 within the second generation in situ
resistive heating element 45.
[0076] When an in situ resistive heating element 40 in electrical
contact with a diverging pair of electrodes 50 is electrically
powered, the in situ resistive heating element 40 may heat and
pyrolyze neighboring subterranean regions, causing an aggregate
electrically conductive zone 48 to expand along the length of the
diverging electrodes. Where the electrodes 50 converge away from
the in situ resistive heating element 40 (i.e., the closest
approach of the electrodes 50 is not within the in situ resistive
heating element 40), the electrical current passing through the
expanding aggregate electrically conductive zone 48, and thus the
greatest resistive heating, may concentrate away from the in situ
resistive heating element 40. Where the electrodes 50 converge
towards the in situ resistive heating element 40, the electrical
current and the greatest resistive heating may concentrate within
the in situ resistive heating element 40. The greater heating at a
shorter electrode spacing may increase the speed of the pyrolysis
and expansion of the aggregate electrically conductive zone 48.
[0077] FIG. 10 illustrates two second generation in situ resistive
heating elements 45 at a point when both might be powered
simultaneously. The electrical polarity and/or electrical phase of
the second pairs of electrodes 52 may be configured to avoid
crosstalk between the upper and lower second generation in situ
resistive heating elements 45. For example, the left electrode 50
of each second electrode pair 52 may share a similar electrical
polarity and/or electrical phase, as indicated by the circled plus
signs. Likewise, the right electrode 50 of each second electrode
pair 52 may share a similar electrical polarity and/or electrical
phase, as indicated by the circled minus signs. If the left
electrodes 50 had roughly opposite polarities and/or phases (e.g.,
180.degree. out of phase), electrical current would tend to flow
predominantly between the left electrodes 50 instead of between
either of the two second electrode pairs 52, owing to the shorter
electrical path length (and hence likely lesser resistance and
higher conductance) between the left electrodes 50 than either
second electrode pair 52. For the example of FIG. 10, upper, lower,
left, and right refer to the figure on the page, not to the
subterranean formation 28.
[0078] FIG. 11 schematically depicts examples of systems 30 for
pyrolyzing organic matter within a subterranean formation 28.
Systems 30 may comprise a first electrode pair 51 electrically
connected to a first generation in situ resistive heating element
44 in a first region 41 within the subterranean formation 28.
Systems 30 may comprise a second electrode pair 52 electrically
connected to a second region 42 within the subterranean formation
28, where the second region 42 is adjacent the first region 41.
Systems 30 may comprise at least one second region 42, and
optionally a plurality of second regions 42, each adjacent the
first region 41 and each electrically connected to a distinct
second electrode pair 52. Further, each second region 42 may
comprise a second generation in situ resistive heating element 45.
Systems 30 may comprise at least one third region 43, each adjacent
at least one second region 42 and each electrically connected to a
distinct third electrode pair 53. Further, each third region 43 may
comprise a third generation in situ resistive heating element
46.
[0079] Each electrode 50 may be contained at least partially within
an electrode well 60. An electrode 50 may extend into the
subterranean formation 28, outside of an electrode well 60, for
example, through a natural and/or manmade fracture. An electrode
well 60 may contain one or more electrodes 50 and other active
components, such as a conventional heating element 58.
[0080] Systems 30 may comprise an electrical power source 31
electrically connected through the first electrode pair 51 to the
first generation in situ resistive heating element 44. Further,
systems 30 may comprise an electrical power switch 33 that
electrically connects (potentially sequentially or simultaneously)
the electrical power source 31 to the first electrode pair 51 and
the second electrode pair 52.
[0081] Systems 30 may comprise a sensor 32 to monitor a monitored
parameter relating to at least one of the subterranean formation 28
and the organic matter in the subterranean formation 28. The
monitored parameter may include geophysical data relating to a
shape, an extent, a volume, a composition, a density, a porosity, a
permeability, an electrical conductivity, an electrical property, a
temperature, and/or a pressure of the subterranean formation 28
and/or a region of the subterranean formation 28. The monitored
parameter may relate to the production of mobile components within
the subterranean formation 28 (e.g., hydrocarbon production). The
monitored parameter may relate to the electrical power applied to
at least a portion of the subterranean formation 28. For example,
the monitored parameter may include the at least one of the
duration of applied electrical power, the magnitude of electrical
power applied, and the magnitude of electrical current transmitted.
The magnitude may include the average value, the peak value, and/or
the integrated total value.
[0082] Systems 30 may comprise a production well 64, from which
mobile components (e.g., hydrocarbon fluids) are extracted or
otherwise removed from at least one of the first region 41, the
second region(s) 42, the third region(s) 43, and/or the
subterranean formation 28. For example, the production well 64 may
be fluidically connected to at least one of the first region 41,
the second region(s) 42, the third region(s) 43, and/or the
subterranean formation 28.
[0083] Systems 30 may comprise a controller 34 that is programmed
or otherwise configured to control, or regulate, at least a portion
of the operation of system 30. As examples, controller 34 may
control the electrical power source 31, record the sensor 32
output, and/or regulate the system 30, the first generation in situ
resistive heating element 44, the second generation in situ
resistive heating element 45, and/or the third generation in situ
resistive heating element 46. The controller 34 may be programmed
or otherwise configured to control system 30 according to any of
the methods described herein.
[0084] In the present disclosure, several of the illustrative,
non-exclusive examples have been discussed and/or presented in the
context of flow diagrams, or flow charts, in which the methods are
shown and described as a series of blocks, or steps. Unless
specifically set forth in the accompanying description, the order
of the blocks may vary from the illustrated order in the flow
diagram, including with two or more of the blocks (or steps)
occurring in a different order and/or concurrently.
[0085] As used herein, the term "and/or" placed between a first
entity and a second entity means one of (1) the first entity, (2)
the second entity, and (3) the first entity and the second entity.
Multiple entities listed with "and/or" should be construed in the
same manner, i.e., "one or more" of the entities so conjoined.
Other entities may optionally be present other than the entities
specifically identified by the "and/or" clause, whether related or
unrelated to those entities specifically identified.
[0086] As used herein, the phrase "at least one," in reference to a
list of one or more entities should be understood to mean at least
one entity selected from any one or more of the entity in the list
of entities, but not necessarily including at least one of each and
every entity specifically listed within the list of entities and
not excluding any combinations of entities in the list of entities.
This definition also allows that entities may optionally be present
other than the entities specifically identified within the list of
entities to which the phrase "at least one" refers, whether related
or unrelated to those entities specifically identified.
[0087] In the event that any patents, patent applications, or other
references are incorporated by reference herein and (1) define a
term in a manner that is inconsistent with and/or (2) are otherwise
inconsistent with, either the non-incorporated portion of the
present disclosure or any of the other incorporated references, the
non-incorporated portion of the present disclosure shall control,
and the term or incorporated disclosure therein shall only control
with respect to the reference in which the term is defined and/or
the incorporated disclosure was present originally.
[0088] As used herein the terms "adapted" and "configured" mean
that the element, component, or other subject matter is designed
and/or intended to perform a given function. Thus, the use of the
terms "adapted" and "configured" should not be construed to mean
that a given element, component, or other subject matter is simply
"capable of" performing a given function but that the element,
component, and/or other subject matter is specifically selected,
created, implemented, utilized, programmed, and/or designed for the
purpose of performing the function. It is also within the scope of
the present disclosure that elements, components, and/or other
recited subject matter that is recited as being adapted to perform
a particular function may additionally or alternatively be
described as being configured to perform that function, and vice
versa.
[0089] As utilized herein, the terms "approximately," "about,"
"substantially," and similar terms are intended to have a broad
meaning in harmony with the common and accepted usage by those of
ordinary skill in the art to which the subject matter of this
disclosure pertains. It should be understood by those of skill in
the art who review this disclosure that these terms are intended to
allow a description of certain features described and claimed
without restricting the scope of these features to the precise
numeral ranges provided. Accordingly, these terms should be
interpreted as indicating that insubstantial or inconsequential
modifications or alterations of the subject matter described and
are considered to be within the scope of the disclosure.
INDUSTRIAL APPLICABILITY
[0090] The systems and methods disclosed herein are applicable to
the oil and gas industry.
[0091] The subject matter of the disclosure includes all novel and
non-obvious combinations and subcombinations of the various
elements, features, functions and/or properties disclosed herein.
Similarly, where the claims recite "a" or "a first" element or the
equivalent thereof, such claims should be understood to include
incorporation of one or more such elements, neither requiring nor
excluding two or more such elements.
[0092] It is believed that the following claims particularly point
out certain combinations and subcombinations that are novel and
non-obvious. Other combinations and subcombinations of features,
functions, elements and/or properties may be claimed through
amendment of the present claims or presentation of new claims in
this or a related application. Such amended or new claims, whether
different, broader, narrower, or equal in scope to the original
claims, are also regarded as included within the subject matter of
the present disclosure.
* * * * *